1. Field of the Invention
The present invention pertains to a novel method for water-granulating calcium ferrite slag produced during copper converting operation.
2. Related Art
In the copper smelting process, high-temperature silicate slag, which may contain, as principal components, 35-40 weight % of FeO, 30-35 weight % of SiO.sub.2, and 3-7 weight % of CaO, is produced in a smelting furnace, while high-temperature calcium ferrite slag (calcium-based slag), which may contain, as principal components, 45-65 weight % of Fe.sub.3 O.sub.4, 10-30 weight % of CaO and 10-35 weight % of Cu.sub.2 O, is produced in a converting furnace. The both types of slag are shattered into granules by bringing them into contact with a large amount of water to effect rapid quenching. This operation is, in general, called "water-granulation" or "granulation".
FIGS. 1 and 2 depict a typical granulation apparatus used for water-granulating the aforesaid slag. The granulation apparatus includes a discharging launder 1 for discharging slag; a receiving launder 2 arranged below the downstream end 1a of the discharging launder 1 so as to extend in a discharging direction of the slag as indicated by the arrow P in FIG. 1; and a water-jetting device 3 for jetting granulating water towards the slag, being discharged from the discharging launder 1 to the receiving launder 2. The water-jetting device 3 is constructed to have a large number of elongated water outlets 3a (see FIG. 2), a water-supplying tubular member 3b connected to the outlets in fluid communication therewith, and a water conduit 3c connected to the tubular member 3b at its lateral side so as to be in fluid communication therewith.
Conventionally, the water-granulation of the silicate slag has been carried out using the aforesaid granulation apparatus in a relatively satisfactory manner. The water-granulation of the calcium ferrite slag has been also carried out by the same apparatus, but has been very difficult. For example, when the operational conditions similar to those of the water-granulation of the silicate slag are adopted for the water-granulation of calcium ferrite slag, phreatic explosions have frequently occurred.